Tetrachloro-butyl secondary phosphites

ABSTRACT

Disclosed are novel tetrachloro-butyl secondary phosphites which are the reaction product of 4,4,4-trichloro-1,2-epoxybutane or 2,4,4,4-tetrachlorobutanol with a phosphorus trihalide. These compounds are useful as flame retardant additives in plastic resin compositions.

This is a division of application Ser. No. 080,744, filed Oct. 1, 1979,now U.S. Pat. No. 4,247,489, which in turn is a division of applicationSer. No. 937,033, filed Aug. 25, 1978, which is now U.S. Pat. No.4,207,272 issued June 10, 1980.

Current and anticipated regulations restricting the flammability ofplastic wares has required the manufacturers of plastic articles toimplement effective ways to fire-retard these materials. Such effortshave produced a variety of fire retardant compounds which can beincorporated into the resin mixtures. Phosphorus and halogen additivecompounds, in particular, have been found to impart favorablefire-retardancy properties.

Novel halogenated phosphite esters have now been developed, according tothe present invention, which are useful as fire retardant additives forvarious plastic compositions. These chlorinated alkyl secondaryphosphites offer a favorable balance of cost, fire retardance, anduseful resin property modification.

The novel compounds of the present invention are secondary phosphiteaddition products of 4,4,4-trichloro-1,2-epoxybutane and2,4,4,4-tetrachlorobutanol with a phosphorus trihalide.

The compound 2,4,4,4-tetrachlorobutanol (TCBA) is a well-known versatilecompound with a wide range of utilities. It can be prepared by variousconventional methods. For example, U.S. Pat. No. 3,399,217 describes amethod for preparation of TCBA by the catalyzed reaction of carbontetrachloride and allyl alcohol. TCBA reacts in a manner typical ofaliphatic alcohols, and, in addition, may be readily dehydrohalogenatedto yield the compound 4,4,4-trichloro-1,2-epoxybutane (TCBO). TCBO is awell-known reactive, high chlorine-containing epoxide useful in thepreparation of epoxy resins, lubricants, polyurethane foams, and thelike. An exemplary method for production of TCBO by dehydrohalogenationof TCBA is described in U.S. Pat. No. 3,923,844.

Secondary alkyl phosphites are commonly prepared by methods known in theart involving reaction of phosphorus trichloride with a primary alcohol(see Noller, Chemistry of Organic Compounds, Third Edition (1966), p.318). Using stoichiometric proportions of reactants, i.e., about 3 molesof alcohol per each mole of phosphorus trichloride, the reaction resultsin the formation of a tertiary alkyl phosphite. In the absence of anamine base to scavenge the liberated hydrogen chloride gas formed duringthe reaction, the tertiary phosphite is cleaved by the action of the HClto produce a secondary phosphite ester.

However, as pointed out in co-pending application Ser. No. 899,919,filed Apr. 26, 1978, it has surprisingly been discovered that in thereaction of TCBA and a phosphorus trihalide, the tertiary phosphiteester formed is not cleaved by the internally generated hydrogen halideunder the normal reaction conditions, without application of externalenergy or increased pressure, and maintains its integrity even in theabsence of an amine scavenger.

According to the present invention, the novel tetrachloro-butylsecondary phosphites can be prepared by a method involving reaction of aphosphorus trihalide with an alkylene oxide or alcohol comprising TCBAand/or TCBO and including a supplemental alcohol or alkylene oxide insubstitution of a portion of the TCBA or TCBO reactant. Thissupplemental reactant forms an ester more susceptible to hydrogen halideattack than the TCBA or TCBO ester group and is selectively cleaved bythe hydrogen halide to readily result in secondary phosphite formation.

More in detail, the reactions by which the present compounds can be madeare represented by Equations I and II below. Equation I representsreaction of two moles of TCBA with one mole of phosphorus trichloridefollowed by addition of one mole of a supplemental alcohol (e.g.,methanol) to produce a mixed tertiary phosphite ester which istransformed into the secondary phosphite by selective cleavage of themethyl ester by the internally generated HCl. The cooling effect of theHCl generated also serves to maintain the exothermic reaction at atemperature low enough to avoid decomposition of the phosphite withoutthe need for external cooling. ##STR1##

Equation II depicts another route for producing the noveltetrachloro-butyl secondary phosphites of the present inventionrepresented by reaction of one mole of PCl₃ with two moles of TCBOfollowed by addition of one mole of a supplemental alcohol (e.g., MeOH)and subsequent cleavage and secondary phosphite formation. ##STR2##

In reaction of TCBO with a phosphorus trihalide, the alkylene oxideserves as a hydrogen halide scavenger in itself, as the hydrogen halideis utilized in the mechanism of reaction, and therefore no excesshydrogen halide is liberated. External cooling is required to maintainthe exothermic reaction at a temperature low enough to avoiddecomposition of the phosphite formed. In order to readily cleave thesupplemental alcohol-ester group, additional hydrogen halide may beintroduced into the reaction to bolster the amount generated from thesupplemental alcohol reaction.

As illustrated, although both alkyl alcohols as well as alkylene oxidesmay be utilized in forming the phosphite esters, alcohols are preferred.The use of alcohols results in hydrogen halide generation which coolsthe reaction and also serves as an internal source of hydrogen halidefor cleavage purposes.

In carrying out these reactions, it is contemplated that any phosphorustrihalide may be employed; i.e., the halide can be chlorine, bromine,iodine or fluorine. However, it is preferred to employ those phosphorustrihalides in which the halogen is chlorine, bromine, or mixturesthereof. Phosphorus trichloride is particularly preferred.

In addition to all TCBO or TCBA secondary phosphites derived fromreaction of two moles of TCBA or TCBO per mole of phosphorus trihalide,novel secondary phosphite esters, according to the present invention,having one or more other constituents can also be readily prepared.

These compounds are represented by the formulae: ##STR3## wherein X is ahalogen; and, each R radical is independently selected from alkyl of 1to about 20 carbon atoms, 2-haloalkyl of about two to about eight carbonatoms, alkaryl, aryl, halogenated aryl, and arylalkyl.

These compounds are prepared by employing reactant combinations of TCBOand TCBA, as well as combinations of other alkylene oxides, alcohols,and phenols with the TCBO and TCBA. At least one mole of TCBO or TCBAper mole of phosphorus trihalide is used, with the remaining one mole ofreactant replaced with other alcohols, phenols and/or epoxides.Accordingly, aliphatic alcohols (with or without heteroatoms, such assulfur, phosphorus, and oxygen) up to about 20 carbon atoms can be used.These typically include methanol, ethanol, butanol, isopropanol,isobutanol, 2-methoxyethanol, TCBA, other halogenated alcohols, and thelike. Supplemental epoxides that can be used are alkylene oxides havinga 1,2-epoxide ring. Illustrative are ethylene oxide, propylene oxide,butylene oxide, pentylene oxide, epichlorohydrin, trichloropropyleneoxide, trichlorobutylene oxide, TCBO, hexylene oxide, octylene oxide,and the like. Usually, these oxides contain from two to eight, and mostpreferably from two to four carbon atoms. Further, phosphites containingalkaryl substituents can be prepared by including alkyl phenol reactantssuch as p-tert-butylphenol, nonyl phenol, 1,2,3 trimethyl phenol, 1,2diethyl phenol, and other derivatives of phenol, naphthol, cresol, BHT,and the like. Halogenated aryl phosphite ester substituents can beaccomplished through use of halogenated phenol reactants such astrihalo-phenol derivatives. Arylalkyl substituents can be made fromreaction with arylalkyl alcohols such as benzyl alcohol, 2-phenylethanol, and other such substituted alcohols of up to about 20 carbonatoms.

In order to accommodate selective cleavage to produce a desiredsecondary phosphite, the supplemental alkyl alcohol or alkylene oxideemployed must be of such a nature so as to form an ester group that ismore susceptible to hydrogen halide cleavage than the desired secondaryphosphite ester groups. Generally, the supplemental alkyl alcohol oralkylene oxide that can be used to carry out the present reactions maybe any such reactant that features a lower chain length than the desiredconstituents. These materials typically include methanol, ethanol,isopropanol, 2-methoxyethanol, ethylene oxide, propylene oxide and thelike.

Although the reaction may be run in the absence of a solvent, it isgenerally preferred to employ a convenient solvent medium. Any inertorganic liquid which is a solvent for both the catalyst and thephosphorus trihalide may be employed for this purpose, such as ethylenedichloride.

The secondary phosphites of the present invention are useful as fireretardant additives and as chemical intermediates for fire retardantadditives for epoxy, polyvinylchloride (PVC), and polyurethane resins.These phosphites further are useful as plasticizers and resinstabilizers. The high chlorine content of these phosphites results ingood organic solubility, decreased water solubility, and goodeffectiveness in fire retardance. The products are also useful asfunctional fluids and lubricant additives.

The following examples are provided to further illustrate the invention.All parts and percentages given are by weight, unless otherwisespecified. Temperatures given are degrees centigrade.

EXAMPLE 1 Preparation of Bis (2,4,4,4-tetrachlorobutyl) phosphite

A total of one mole distilled TCBA was added dropwise to a well-stirredsolution of 0.5 mole phosphorus trichloride. The temperature of thereaction was lowered by the escaping HCl gas. The mixture waspost-reacted for about two hours at room temperature, and was thentreated dropwise with 0.5 mole methanol. The temperature of thewell-stirred mixture was kept below 35° during the addition with the aidof an ice-water bath. This final solution was post-reacted for about 30minutes at room temperature. The HCl vapors were removed by stirring forabout one hour under reduced pressure. Residual acidity was neutralizedby the addition of 0.5 ml triethylamine. The colorless product thusformed was obtained in 98 percent yield. The nature of the product wassubstantiated by infrared, nuclear magnetic resonance, and elementalanalysis. At least 61 percent of the material was the expected secondaryphosphite, about 29 percent was the tertiary TCBA phosphite.

Calcd, for C₈ H₁₁ Cl₈ O₃ P: %Cl, 60.43; %P, 6.60. Found: %Cl, 60.67; %P,6.47.

What is claimed is:
 1. A tetrachloro-butyl secondary phosphite havingthe formula: ##STR4## wherein X is a halogen, and R is selected fromalkyl of 1 to about 20 carbon atoms, 2-haloalkyl of about 2 to about 8carbon atoms, alkaryl, aryl, halogenated aryl, and arylalkyl.
 2. Thecompound of claim 1 wherein R is 1,4,4,4-tetrachloro-2-butyl.
 3. Thecompound of claim 2 wherein X is chlorine.